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- procedure a(const a:string);一般这样形式的过程前辈门是怎样用那个(const a:string);参数的
------------------------------
Type Switch
Syntax {$J+} or {$J-}
{$WRITEABLECONST ON} or {$WRITEABLECONST OFF}
Default {$J-}
{$WRITEABLECONST OFF}
Scope Local
The $J directive controls whether typed constants can be modified or not. In the {$J+} state, typed constants can be modified, and are in essence initialized variables. In the {$J-} state, typed constants are truly constant, and any attempt to modify a typed constant causes the compiler to report an error.
Writeable consts refers to the use of a typed const as a variable modifiable at runtime. For example:const foo: Integer = 12;
begin
foo := 14;end.With $WRITEABLECONST OFF, this code produces a compile error on the assignment to the foo variable in the begin..end block. To fix it, change the const declaration to a var declaration.In early versions of Delphi and Borland Pascal, typed constants were always writeable, corresponding to the {$J+} state. Old source code that uses writeable typed constants must be compiled in the {$J+} state, but for new applications it is recommended that you use initialized variables and compile your code in the {$J-} state.